Boiler



June 30, 1959 J. w. BROWN, JR., ET AL 2,892,451

BOILER 3 Sheets-.SheetV 1 l Filed Dec. 2. 1954 nmA INVENToRs JOHN w. BROWN, JR. BY ARVID CK.NIHLEN 3 Sheets-Sheet 2 June 30, 1959 JQW. BROWN, JR., ET AL BOILER Filed De'c. 2. 1954 June 3.0,l 1959 J. w. BROWN, JR., ET AL 2,892,451

BOILER 3 Sheets-Sheet 3 .Filed Deo. 2. 1954 BRowN, JR.

ATTORNEYS INVENTORS JOHN W.

United States l l invention relates' to steam boilers; and I more par ticularly to re-tube boilers adapted to burn gaseous or liquid'fuels.

A general'objectof theinvention isf the provisionof eilicient steam boilers which have' a' liighcapacityforf the generationof' steam in comparison with` their overall dimensions'. Other objects Aincludethe provisionofsteam boilers irrwhich'localizedl overheating and? depositsl of boiler scale are prevented by forced circulationwithi the boiler andfthe useof` finned tubes-to increase lheat transfer, the provision of boilersv having radiant sections and convectionse'ctionsinwhich tlle'lluegases are-cooled in the radiant sections to-"su'el'r a'nV extentthat thereis less likelihood Aof damage to the lire tubes in'th'ecoiivection sections, and the" provision of* dnrable and reliable steamV boilers which be manufactured atA vrez'tsonable CONS Preferredform's of" boilers'l embodying the invention aref showninth'e accompanying; drawings; in' which;

FigureV 1` is a longitudinall section through`v` oneJ forni: of

boiler embodyinggtheinventiir;

Figure Y2 is an end elevation oftle boiler showni'n Figure 1.

Figure-3 is aA fragmentary transverse'sectiii' taken's' indicatedby the line*3i '-3fofFi`gure1.

Figure 4f isafragmentary longitudinalsetion showing another form' offboile`r'embodying the iveiiti'oi Figure 5 isa fragmentary transverse section taken 4along lihetSLSofFigure-l; andi Y Figure `6"is a fi*'a'gmentarylongitudinalSection1 showing still anotherfonrrof'boiler embodyingthe'invention; Assliownpartioul'arly in' Figures 1', 2`aiid 31, apreferred form 'of' boilerk embodying oiiry invention may comprise a shelll 10',` ttlie= oppositie`4 ends off'wliicli are welded tube sheets 12 and 14. A large combustion tube 15 exi tends between and is Weldedfto-thef tubejsli'eetsl.- At'the front of thezboilenmendi portion I6of=`itube 1-3"1 projects beyond. tube? sheet: and. acts1as` supportfoi any convenient" form:` of; burner,n suchv asA the;v gasj` yburner 18; the burner may be supplied with air- .byf' means of `blower L9. @ombustioru of the'ffileli takesplace. within thecombustiony tube 15; thezihotzproductsof combustion traveling; in the direction.` indicatedl by the arrows in Figure. 1 Y

t, Inl order tovincrease the@ eciency of heat' transfert in the combustion tube which: constitutes:the3radiant-secf tion ofi the boiler,k the tube isprovidedf with', external; longitudinally extending iins 20 which'` extend? furthe greater portionof the length of thel tube I'SrY between the headers 12 and 14. Fins 2li-are preferably: welded tothe exterior ofthe tube`A 1i in. the manner. disclosed in the prior patent of John W. Brown, Jr., No. 2,2'6r1',13:7', issued: November: 4, 1941.' Finned= tubes made according to the aforesaid patent have excellent heat. exchange chaiL acteristics because ofY the nature ofthe paths foriow of. heat between` the tube andthens. l CombustionggasesJ discharged, from; the rear end 22 of? they tubeV 15 fiow'viuto theI reanhousingg member.- 23 t 2,892,451 Patented June 30, 1959 ice wliiohis'bolted as at 25 to a flange 26 welded to the `tube 4sheet14'. Housing member 23 is preferably lined @with a refractory'material` 27, as shown. The hot'combustion gases discharged into housing 23 are reversed in direction andl f low vtoward the front or. stack end tbe'boiler through the lire tubes 30 which extend between thetube sheets 12y and 14 and are rolled into the tube sheets in the usual manner. In order to increase the efficiency of heat transfer between the ue gasesand the lire tubesiall,` the tubes are preferably providedwith internalfins31; internally finned tubes such as shown il'rtliepending application of Gaddis; Myers and Welsh', Serial No. 181418,l filed-September 18, 1950, now Patent No'. 2,731,709, and owned by the assignee of the present application,- are satisfactory.

From the lire tubes 30 the combustion gases are dis,- charged' into a front` housing 33;` the upper surface of the' housing, as shown particularly in Figure 2, is a'llat p late34 vtowhichthe flue connection 35 is secured.. Hons',- ing33 ispreferably lined with refractory material' 36 and is bolted as at 37to a llange 38 welded to the tube vsl`=.et12.` Y

'Phe boiler is provided with the usual gauges and controls, steam is dischargedtfrom the boiler through the "cjiitlettlil,l and Vfeed Water is supplied thereto by means o fj'a feed' water pump 41" connected to the supply conduit blowdouvnv connection 44 is'provided at the bottom of theV lshell 10,` andthe entire shell is enclosed in ya s hea1 3l1j insulating material' 46` disposed betweenthei shell and the sheath. The boiler is mounted on' th ejsupporting structure indicated in generalV at 47"; thisj'm'ayfbe' off any convenient design and construction. order: toj increase the rate of heat transfer in the radiant section constituted by the externally finned 'com bustier; tube 15; circulation is constantly maintained in the-boiler by means of a circulating pump 48 which draws water in from the upper portion of the boiler through v'the flared end49 ofl conduit 50 andi discharges it through the open end 51 of conduit'52withinthe interior shroud or'tub'e 5'4 Shroud5v4fsurrounds the ins on the exterior of tube 15 and is provided with a ange 5S which is secured as by Welding to the inner surface of the tube sheetlZ'. The opposite end 56 of shroud^54 extends near to; but is'.spaced` from the tube. sheet 14, leaving a space 57j as' sho wn in Figure 1; In addition to the support given by ange 55, the shroud is supported and centered with respect to the finned tube 15 by studs 58 welded tot tbe interior of the shroud and engaging the exterior 'of-j tlie tube. p

InI operation, feed water delivered to the boiler by the feed water pump 41 is discharged into the boiler tlirough the end 51 of tube52 into` the interior of shroud 5'4. Al'so, additional water drawn from the` upper portionofthe boiler throughv conduit 50 is discharged by pump 48 into the same region. The water so pumped into 4the space between the exterior of the combustion tubek 15 v and theinterior of the shroud 54" distributes itself annularly around the tube 1S inthe space 60before tle beginning of the ns 20, and then Hows longitudinally along the iins 20 within the shroud 54 and is discharged through the annular space 57 adjacent the tube sheet 14. Because of the extended surface area provided by the 1ins20 and because of the ow of water along the' lin-si heat isextracted rapidly from the tube 15` and tlie tube is maintained at a temperature considerably below the temperature that would obtain if the tube did not have external fins and if there were no forced circulation of water.

t Important advantagesflow from the reduction in terrii perature of thegcombustion tube 15; the tube is enabled to: extract more heat froml the combustion gases flowing p through` it; corrosion andV damage of the tube byl the combustion gases is reduced; the circulation prevents the occurrence of localized hot spots, and the deposition of solids on the external surface of the tube under ordinary operating conditions is substantially eliminated. For these reasons, the tube is less likely to burn out, and the eiciency of the tube is maintained for long periods of time. Large amounts of heat are removed from the combustion gases in the radiant section without requiring the radiant section to be of undue length, and the gases are discharged at reasonable temperatures into the housing 23. The gases then flow back from the housing 23 through the iire tubes 30, and here the internal fins 31 provide extended surface area, which results in elcient heat interchange between the flue gases and tubes so that a comparatively small number of relatively short fire tubes can extract sufficient heat from the Hue gases to bring them down to the desired discharge temperature.

The circulation of the water within the boiler has a further important advantage at the inner surface of the tube sheet 14. The water discharged from the shell 54 impinges against this surface and constantly washes it, thereby preventing liming at this point. The circulation of water in combination with the reduced temperature of discharge of the combustion gases from the radiant section of the combustion tube 15 thus act together to prevent liming of the boiler and burning out of the fire tubes 30.

In the modified forms of the invention shown in Figures 4, 5 and 6, the boiler is constructed generally the same as the boiler shown in Figures 1, 2 and 3 and parts that are identical with parts shown in Figures 1, 2 and 3 have been given the same reference characters.

In the form of the invention shown in Figures 4 and 5, the shroud 61 is spaced from the front tube sheet 12, as indicated at 62, and is spaced from the rear tube sheet 14, as indicated at 63. The front end of the shroud is preferably flared slightly, as shown at 64, and the shroud is supported on and centered with respect to the combustion tube 15 by means of studs 65. At the rear end of the shroud, projections 67 engage the inner surface of the tube sheet 14 to locate the shroud longitudinally with respect to the combustion tube 15.

.4 shroud, continuing out into the boiler proper through the spaces 72 and 73. The finned members 20a on the exterior of tube 15 do not extend through the central portion 78 of the combustion tube 15, so that the central portion 78 acts as a distribution zone in which the water discharged from the pipe 53 can flow annularly around the tube 15 and distribute itself along the channels provided by the tins. In this form of the invention there is forced circulation to the front of the boiler as well as to the rear, and water is circulated along the interior surfaces of both tube sheets 12 and 14. Also, in this form of the invention, the circulation of the water along the front half of the combustion tube 15 is counter to the ilow of combustion gases therein.

In all of the forms of the invention the forced circulation of the water and the finned combustion tube prevent the combustion tube from reaching excessive temperatures, enable the combustion tube to abstract large quantities of heat from the gases passing therethrough, and thus make the combustion tube into an extremely eilicient radiant heat transfer section. Because of this construction, boilers embodying the invention have high capacity for their size, are durable and reliable because of the elimination of difficulties due to deposition of solids and to corrosion of the re tubes, and are efficient in their utilization of fuel.

Various changes and modifications can be made in the invention without departing from the spirit and scope thereof. The essential characteristics of the invention are dened in the appended claims.

We claim:

1. A fire tube boiler comprising a shell, a front tube sheet and a rear tube sheet secured to said shell, a combustion tube extending through said shell in the lower portion thereof and secured to said tube sheets, a plurality of tire tubes extending between said tube sheets within said shell, a housing at the rear end of said shell adapted to direct products of combustion from said corn- In order to provide for circulation through the shroud v and on the exterior of the iinned tube 15, conduit 52, which, as shown in Figure l, receives the discharge from the circulating pump 48, is connected to a ring or manifold 68 which surrounds the combustion tube 15 in the space 62. Manifold 68 is provided with a series of discharge nozzles 69 which project slightly within the flared end 64 of the shroud 61 and are arranged to discharge streams of water into the interior of the shroud toward the rear of the boiler. The discharge of water in this zone creates circulation in excess of the volume of water discharged by the nozzles because of the injector effect which causes water to be drawn from the main body of water in the boiler into the ared end of the shroud. The operation of this form of the invention is essentially the same as that previously described, except that this arrangement provides additional circulation of water along the interior surface of the front tube sheet 12.

Figure 6 shows a further modification of the structure of circulating water over the exterior of the combustion tube 15. In this form of the invention the shroud 71 preferably consists of a cylindrical tube spaced from both tube sheets 12 and 14 as indicated at 72 and 73. The shroud is centered and supported on the tube 15 by studs 75 and is positioned longitudinally by extensions 76 and 77 which engage the inner surfaces of the tube sheets 12 and 1 4, respectively.

In this form of the invention the discharge from the circulating pump 48 through the pipe 52 is conveyed by conduit 53 to the center of the shroud 71, so that the circulating water is discharged centrally of the shroud and of the tube 15. The water flows in both directions from the point of discharge to the opposite ends .of the bustion tube into the rear ends of said tire tubes, a shroud within said shell and surrounding said combustion tube, said shroud extending for the major portion of the length of the combustion tube and having an open end whereby the interior of said shroud is in direct open communication with the interior of said shell at said open end of the shroud and immediately adjacent one of said tube sheets, and a pump for continuously circulating water primarily longitudinally along said combustion tube within said shroud and discharging at least part of said circulated water at said open end of said shroud into the main body of iiuid within the shell immediately adjacnt and in a direction toward said last mentioned tube s eet.

A2. A boiler according to claim 1 wherein the water discharged by the pump is withdrawn from said boiler at a level above said combustion tube and is discharged into said shroud adjacent the end thereof opposite the said open end thereof.

3. A boiler according to' claim 1 wherein the other end of said shroud is also open and in open communication with the main body of water within said shell, and wherein said pump delivers water to a series of nozzles disposed around said combustion tube adjacent one end thereof and directed to the space between said shroud and said combustion tube and toward the opposite end of said combustion tube.

4. A boiler according to claim 1 wherein the pump discharges water into the central portion of said shroud, the water being discharged therefrom at both ends thereof.

5. A re tube boiler comprising a shell, a front tube sheet and a rear tube sheet secured to said shell, a cornbustion tube extending through said shell in the lower portion thereof and being secured to said tube sheets, the major portion of the length of the exterior only of said combustion tube between said tube sheets being wwf provided with longitudinally extending horizontal fins, a plurality of re tubes extending between said tube sheets within said shell, a housing at the rear end of said shell adapted to direct products of combustion from said combustion tube into the rear ends of said tire tubes, a shroud within said shell and surrounding said combustion tube, said shroud extending for the major portion of the length of the combustion tube and stopping short of one of said tube sheets to provide a discharge opening providing direct communication between the interior of said shroud and the interior of said shell at one end of the shroud and adjacent said last mentioned tube sheets, and a pump for continuously circulating water primarily longitudinally along said combustion tube within said shroud and discharging at least part of said circulated water through said discharge opening adjacent and in a direction toward said last mentioned tube sheet.

6. A re tube boiler comprising a generally cylindrical horizontal shell, a front tube sheet and a rear tube sheet secured to said shell, a combustion tube extending horizontally through said shell in the lower portion thereof, said combustion tube being secured to said tube sheets and projecting beyond said front tube sheet, the major portion of the exterior only of the length of said combustion tube between said tube sheets being provided with longitudinally extending ns, a burner mounted on the projecting portion of said combustion tube and adapted to discharge hot products of combustion into said combustion tube, a plurality of internally nned re tubes extending between said tube sheets within said shell, a housing at the rear end of said shell adapted to direct products of combustion from said combustion tube into the rear ends of said tire tubes, a housing at the front end of said shell adapted to convey products of combustion discharged by said tire tubes to a due, a shroud within said shell and surrounding said combustion tube, said shroud extending for the major portion of the length of said combustion tube and terminating short of said rear tube sheet to provide a zone of open communication between the interior of said shroud and the interior of said shell adjacent said rear tube sheet and a pump for circulating water primarily longitudinally along said combustion tube within said shroud and discharging at least part of said circulated water from said shroud adjacent and in a direction toward said rear tube sheet through said zone of open communication.

References Cited in the file of this patent UNITED STATES PATENTS 434,656 Cunningham Aug. 19, 1890 472,731 King Apr. 12, 1892 813,918 Schmitz Feb. 27, 1906 1,751,534 Taylor Mar. 25, 1930 1,822,871 Morley Sept. 8, 1931 1,838,105 Murray Dec, 29, 1931 2,080,404 Hunter et al May 18, 1937 2,448,128 Trageser Aug. 31, 1948 2,586,998 Schlenz Feb. 26, 1952 2,649,285 Brown Aug. 18, 1953 2,656,821 Ray Oct. 27, 1953 2,704,534 Dalin et al. Mar. 22, 1955 2,710,057 Basset et al June 7, 1955 FOREIGN PATENTS 965,609 France Sept. 18, 1950 7,861 Great Britain Apr. 13, 1905 423,337 Great Britain Jan. 30, 1935 

